A membrane electrode assembly (MEA) included in a unit cell of a fuel cell has a polymer electrolyte membrane where a catalyst layer is disposed, and a frame-shaped gasket disposed on both surfaces of the polymer electrolyte membrane. The gaskets are positioned so as to surround the catalyst layer of the polymer electrolyte membrane, and thus functions to prevent a fuel gas and an oxidizer gas supplied to the catalyst layer from leaking externally.
However, when the gaskets are disposed on both surfaces of the polymer electrolyte membrane and are attached thereto, if bubbles remain between the gaskets and between the gasket and the polymer electrolyte membrane, they become a factor causing a gas leak in the manufactured membrane electrode assembly. On the other hand, a resin sheet having a through hole is known (for example, see Japanese Patent No. 4898221).
However, the resin sheet according to Japanese Patent No. 4898221 is not intended to be used for a gasket, and even though it is applied to the gasket of the membrane electrode assembly, it is difficult to suppress the remaining bubbles. Hence, there is a concern that the fuel gas and the oxidant gas supplied to the catalyst layer leak out externally because a region which is surrounded by the gasket is communicated with a region which is positioned outside of a peripheral edge of the gasket via the remaining bubble, or because the remaining bubbles form a raised portion in the gasket, and thus, the adhesion properties of the gasket and a separator are reduced.